Boron nitride thin films could be deposited on Si(001) by chemical vapor deposition (CVD) at atmospheric pressure using a single source precursor. IR absorption spectra of films deposited between 750 and 1000 o C using B[N(CH 3 ) 2 ] 3 (tris(dimethylamino)borane, TDMAB) as the boron and nitrogen source showed a peak absorption at ~1360cm - 1 characteristic of the in-plane vibrational mode seen in h-BN. It was noted that the mode at 800cm - 1 is very weak. The observed growth rate varied exponentially with temperature in the range 850-900 o C. Ellipsometry measurements were used to investigate the thickness and optical constant of the films. The refractive index, slightly lower than the bulk material, is close to 1.65-1.7 depending on the surface morphology of the films. The surface morphology of thin layers has been observed by atomic force microscopy with an increase of the surface roughness from 0.3 to 3.5nm as the growth temperature increases from 800 to 950 o C.